Vaccum doesn't work/no movement or suction when filter is set to full vaccum

[qwertyuiop]

So I've had a lot of problems with my filter and pump. I have backwashed and took out my DE grids and cleaned them down and my pool system still seems very weak. The pressure of my tank is unusually high (20-25) after backwashing. One thing I have noticed is that my vacuum does not work at all if I set the system to full vacuum. If I set it on half skimmer half vacuum it barely works and is slow, but is actually moving as compared to when it is set on full vacuum. I have changed some of the orings in case of any leaks but I can't seem to find the issue. If you look in the drain skimmer basket while it is set on just vacuum you can barely see the water moving, so I am sure it is an issue with my pump/filter system and not the vacuum.
Any help would be appreciated.

 

[zea3]

Has it always had this problem or is this more recent?

 

[qwertyuiop]

It's more recent in the last like 4-5 months, the vacuum used to be pretty strong and actually had suction.

 

[zea3]

There may be some obstruction in the impeller or the intake from the skimmer pipe. Open up the pump pot and empty out the strainer basket. Make sure the power is shut off and feel for any debris caught in the impeller.

 

[borjis]

Does your pump sound like it's straining/having difficulty pumping while on full vacuum?

 

[qwertyuiop]

Does your pump sound like it's straining/having difficulty pumping while on full vacuum?

Yes it sounds like it's working really hard but you can't really hear that flowing water sound.

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If there was something in the impeller wouldn't it affect the drain too and not just the vacuum?